Wheelchair lift

ABSTRACT

A wheelchair lift system enabling wheelchair accessibility between stair levels for persons incapable of traversing stairs under their own power. The key of the invention is a free-rolling, wheeled platform suspended between two arcuate tracks which are lifted and lowered by synchronized, reversible, worm-gear drive mechanisms. The platform and tracks are mounted on a frame in which also resides peripheral equipment needed to raise and lower the system. A seven-foot-high portal frame supports the drive mechanism which comprises pivoting, worm-gear type drive motors, turning long worm-gears extending vertically downward from the top of the frame to the floor and engaging pivoting worm-gear heads that are attached to the arcuate tracks, while allowing normal access to the stairs.

This is a continuation-in-part of application Ser. No. 268,860, filedJun. 30, 1994, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wheelchair lift system facilitatingtransit between different horizontal levels for persons otherwise unableto make the transit unassisted. A particular embodiment of thisinvention is coupled to stairways and is used to accommodate personsincapable of traversing stairs unassisted. More particularly, thisinvention allows for a safe transit up or down a stairway for thosepersons who are capable of traveling about on a level floor yet havedifficulty negotiating stairs, such persons including but not limitedto, cardiac patients, "walker" patients, and patients in wheelchairs.Yet more particularly, this invention relates to a novel system allowingfor the smooth transit between horizontal elevations using a rollingplatform in conjunction with tracks which are varied in elevation bymeans of a motor coupled to the tracks without using cables, a motorthat can be activated by a wheelchair occupant or other user without anyassistance. Most particularly, the preferred embodiment of the presentinvention uses worm-gears arrayed in such a way as to allow for a safereturn to the lower level in the event of a power failure. Finally, thewheelchair lift system of the present invention, when installed on astairway as to the preferred embodiment, does not prevent that stairwayfrom being traversed in its normal manner.

2. Description of the Prior Art

Motorized lift systems for stairways have been around for a long time,serving to transport persons incapable of otherwise negotiating stairs.Most such systems had to be custom-made for particular locations andstairs. For instance, the most common lift system for transportingpersons up a set of stairs used a fixed rail which in turn was attachedto a stairway wall somewhat like a very strong bannister. The fixed railwas custom-manufactured to fit the entire run of stairs upon which itwould be used. A lifting chair was attached to the rail and the chairmoved between levels using a motorized cabling system or using adirect-drive motor attached to the chair itself. For a wheelchair-boundperson, this system required, generally, that the person be physicallytransferred out of a wheelchair and into the movable chair, and then,after the person traversed the stairs, that he or she be removed fromthe lift chair and placed into either a second wheelchair or into thefirst wheelchair which would have been carried by an attendant thelength of the stairway.

More recent lift systems have been devised that are portable,self-contained devices adaptable to almost any stairs encountered. U.S.Pat. No. 3,229,788 (1966, Booth) teaches such a system. Booth provides awheelchair-supporting platform riding on wheels engaged in a track andcontrolled by a motorized cabling system. For motive force, Booth usestwo reversible electric motors. Each motor is connected to a reductiongear box coupled to the axle of a drum onto which is affixed one end ofa cable. This cable is then threaded around a series of pulleys,including those rotatably mounted to a wheel axle of the platform, andsecured to the upper end of the track on which the wheels rest. In orderto lift the platform along the track, the drum is rotated so as to drawthe cable shorter. The entire system of motors, gear box, and pulleys issecured to the lifting platform.

Another system, more closely antecedent to the present invention, isthat of U.S. Pat. No. 4,674,601 (1987, Benjamin). Benjamin describes anapparatus for enabling wheelchair-confined individuals to more easilyconvey themselves between two different elevations, especially betweenthe inside ground level of a house and the outside ground level. The keyto Benjamin is a unitary molded arcuate lift or scoop on which thewheelchair rides while being conveyed between the two levels. As thescoop rotates up, the wheelchair rolls forward and eventually onto theupper level. The scoop is mounted in a frame in which also resides theperipheral equipment needed to effect the scoop's raising and lowering.The lower end of the scoop in Benjamin is attached to a pair of cableswhich pass up to and through the top of the frame and then aroundtake-up reels. The opposite end of the scoop is attached by a hinge tothe frame at the level of the higher elevation.

Problems associated with the earlier systems include expense andlead-time requirements inherent in custom-made apparatus, complexity ofthe portable cable-based devices, and, in the case of the arcuate systemof Benjamin, the need to keep the wheelchair unlocked during use. Eventhough the portable system of Booth does not require the excessive leadtime and high monetary outlay of the custom-made systems, it has othersignificant problems. For example, the large number of pulleys requiredfor motor-torque reasons in systems such as that of Booth increases thelikelihood of component failure and consequent down-time. Furthermore,where, as in Booth, all of the components are secured to the platform,any repair to the motor, cable, or pulleys requires the disassembly ofthe platform for access. Although one of the touted advantages of Boothis its portability, nevertheless, from a practical viewpoint, the weightof two synchronized motors, two reduction gear boxes, multiple pulleys,cables, tracks, support members, and platform make the system somewhatburdensome to transport, to say the least.

The molded, arcuate lift system of Benjamin suffers a major regulatorydisadvantage. For it to work properly, the wheelchair must befree-rolling; that is, the wheelchair wheels must not be locked.Although this system should be quite safe, it confronts a regulatorybarrier in the widespread requirement that wheelchair wheels be lockedduring transit of the wheelchair between different levels.

Therefore, what is needed is a wheelchair lift system combining thesturdiness of a fixed system, the minimal manufacturing lead time of aportable system, and the simplicity of an arcuate molded platform liftsystem, while readily complying with the existing regulatory framework.What is further needed is such a system that can be installed in astairway without precluding normal access to that stairway. What is yetfurther needed is such a lift system that utilizes only a small numberof components and that utilizes standardized components, so as tominimize breakdown frequency and also the attendant down-time whenbreakdown does occur.

SUMMARY OF THE INVENTION

The wheelchair lift system of the present invention combines thesecurity and stability of fixed lift systems with the standardization ofcomponents and ease of adjustment and assembly of a portable,cable-based lift system. The heart of the invention is a free-rollingwheelchair-supporting platform mounted on and extending between twoarcuate tracks. The raising and lowering of the platform is achieved byraising and lowering the pair of arcuate tracks. If the system isinstalled in a stairway, full access is provided to the stairway whilethe arcuate tracks are in their lowered position, which is their normalrest position.

In addition to the platform and arcuate tracks, the lift system of thepresent invention consists of the peripheral equipment needed to supportthe tracks and to vary their elevation. This includes in particular aspecially-designed steel portal frame which typically would consist oftwo trapezoidal side supports vertically connected to a top connectionplate. This portal frame is secured to the floor on the lower level andconstitutes the backbone support of the entire system. Two drivemechanisms, used for lifting and lowering the tracks, are secured topivoting bracket assemblies. The drive mechanisms may have cable means,worm-gear means, or any other suitable means for achieving the raisingand lowering of the tracks. The pivoting bracket assemblies are attachedto the top connection plate, one directly above each side support. Eachdrive mechanism extends vertically downward on the outside of the portalframe supports. These drive mechanisms use pivoting joints to attach tothe two arcuate tracks. Each track is located on the inside edge of aside support and is rotationally secured to a steel bracket located justbelow the upper level. The portal frame has openings cut into each sidesupport through which the pivoting joints connect each track to itsrespective drive mechanism. The location and size of the openings in theside supports allow for the required vertical and horizontal movement ofthe respective pivoting joints when the system is in use. When thesystem is activated, the synchronized drive mechanisms raise or lowerthe tracks upon which a free-rolling platform rides in a steady,controlled fashion. The platform may be designed in a variety of ways,including an essentially flat plate having platform wheels that arerotatably attached to the platform by way of a support bracket. In thatdesign the support bracket is secured to the platform on one end and hasan axle on a second end to hold and support the wheels. The wheeledplatform can use a variety of wheels such as metal or synthetic,ball-bearing, or any combination of wheel characteristics to achieve thedesired smoothness of roll. One method of effecting the desiredsmoothness of roll would utilize a torsion mechanisms within the wheels.In the event of power failure, the drive mechanisms allow for a safe andcontrolled return to the lower level. Alternatively, the platform may bejoined directly to the arcuate tracks, with the platform conforming tothe change in the tracks, much like a roll-top desk.

To change from a lower floor level to an upper floor level by means ofthe Wheelchair Lift, the wheelchair-bound user first lowers the platformif the Wheelchair Lift is in the upper position. This is accomplished byany of a number of methods. One is by the use of a microwave-controlleddevice similar to that used on "radio-controlled" garage doors. Anothermeans could be a simple electrical switch, or any other suitable means,as would be understood by those skilled in the art. Once the platform isin the lowered position, the wheelchair is rolled forward onto theplatform. After locking the wheelchair wheels, the wheelchair-bound userthen activates the system. Once activated, the system's synchronized,reversible, drive mechanisms cause the tracks and the attached, platformto rise. The system is designed to move sufficiently slowly and witharcuate-shaped tracks so that the free-rolling platform will slowly rollalong the tracks, naturally seeking its lowest possible position.Consequently, the platform will roll slowly and smoothly along to theend of the side tracks until the platform is stopped by the upper-levelfloor. In order to prevent the platform from moving away from theupper-level floor, the tracks are kept at a slight upward angle relativeto the upper-level floor when in the raised position. Once thewheelchair lift reaches its uppermost point, the system stops and thewheelchair-bound user can then unlock the wheels on the chair andproceed forward onto the upper level.

To return to the lower level, a similar procedure as that describedabove is followed. Forces similar to those governing the raising processcause the platform to slowly roll along the tracks as the tracks arelowered. When the system reaches its lower position, the rollingplatform is stopped by a plate connecting the ends of the arcuatetracks. While the wheelchair lift system is in the lowered position, theconnecting plate rests on the floor and is level with the rollingplatform. In an alternative embodiment of the invention, the combinationof the arcuate tracks and the wheelchair-supporting platform may bemoved using a set of hydraulic cylinders that effectively replace theportal frame so as to permit easier access to the stairway by personsnot needing the wheelchair lift. Each of the hydraulic cylinders isattached at one end to a corresponding stationary support bracket thatextends along the stairs essentially from top to bottom. The other endof the hydraulic cylinder is attached to a side wall that is in turnconnected to one of the arcuate tracks, each arcuate track having itsown side wall. The side walls are in turn connected to a pivot bracketlocated at the upper region of the stairway such that when the hydrauliccylinders are operated, the side supports pivot upward or downward. Inan optional design of the device using the hydraulic lift, the two sidewalls which are coupled together can be moved using a single hydrauliccylinder. The single hydraulic cylinder is affixed to one of the sidewalls and to a single stationary support bracket located on one of thetwo track sides.

This alternative design using standard hydraulic components and motorand pump units is robust and provides a supplemental factor of safety inthe overall design of the system. In addition, the side walls may bedesigned of sufficient height to provide added safety by constrainingthe user within. That height need be no more than approximately threefeet--about the height of a wheelchair--such that the user will besecure and yet will be permitted to observe the area beyond the sidewalls.

In summary, the present invention includes a steel portal frame tosupport the drive mechanisms and side tracks, a free-rolling platform,and a support bracket. Such a design allows access in particular via astairway to a different floor level for mobile-restricted persons whilestill allowing normal use of the stairway by other people. Furthermore,the track system allows for cutting the length of the tracks in thefield for instant adaptability to any particular stair elevations orwhere, absent any stairs, a transition between levels is required. Theheight to be traversed is limited only by the overhead clearance of aparticular location, the length of the uncut tracks, and the height ofthe portal frame. In an alternative arrangement, the combination of ahydraulic lift system and side walls coupled to the arcuate tracks isused to replace the portal frame and drive mechanism. This alternativearrangement provides easier access to the stairway by able-bodiedpersons and more security to the left users.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the wheelchair lift of the presentinvention showing the platform in its lowered position.

FIG. 2 is a three-positioned, diagrammatic side elevation view of thewheelchair lift of the present invention showing standard ramprequirements and positioning on a stairway.

FIG. 3 is an enlarged, three-positioned, side view showing the positionof the invention's worm-gear and platform position during lifting and/orlowering of the side tracks.

FIG. 4 is an end view of the apparatus showing the platform of thepresent invention in its lowered position.

FIG. 5 is a diagrammatic side view of the alternative wheelchair lift ofthe present invention, showing the side-wall-and-hydraulic-cylinderassembly in the raised position.

FIG. 6 is a diagrammatic side view of the alternative wheelchair lift ofthe present invention, showing the side-wall-and-hydraulic-cylinderassembly in the lowered position.

FIG. 7 is an end view of the alternative wheelchair lift showing therolling platform in the lowered position.

PREFERRED EMBODIMENT

The general operation of the preferred embodiment of the presentinvention is illustrated in FIG. 1 and FIG. 2 which shows a wheelchairlift system 10 positioned adjacent to stairway 12 and generally restingon floor 14. FIG. 3 shows simultaneous views of the different positionsof a drive mechanism 80 having a first worm-gear 24, a first drive motor26, a first pivoting, threaded worm-gear head 30, a left side arcuatetrack 19, and a platform 22 having means for traversing the left sidetrack 19 and a right side arcuate track 19' and in operative engagementtherewith. FIGS. 2 and 3 also show the system 10 with the platform 22located at the top of the stairway 12 and on the floor 14. FIG. 4 showsan end view of the wheelchair lift system 10 in its lowered positionwith a cut-away view of the first drive motor 26 having a drive shaft27.

The wheelchair lift system 10 includes a specially-designed steel portalframe 16 comprising a trapezoidal left side support member 17 and atrapezoidal right side support member 17' vertically connected to a topconnection plate 18. The portal frame 16 is permanently secured to thefloor 14 providing stability for the left track 19, the right track 19',and a mounting position for the first drive motor 26 and a second drivemotor 26'. The left support 17 and the right support 17' are fabricatedfrom 1/4" thick steel plate having a base that is wider than the topwhere connection plate 18 is attached. The trapezoidal shape of the leftside support 17 and the right side support 17' give greater stabilityunder shifting loads during use. An example of an acceptable trapezoidalsupport dimension would be 18" wide at the base, 8" wide at the top, and7" high. As will be clear from the following descriptions, the height ofthe portal frame 16 is important for allowing use of the stairway 12when the wheelchair lift system 10 is in the lowered position and not inuse.

Except for worm-gear access means to be described herein, the firstworm-gear 24, a second worm-gear 24', the first driver motor 26, and asecond drive motor 26' are preferably enclosed in housing means, asillustrated. The left support 17 has a left opening 34 providing accessto the first worm-gear head 30 and the right support 17' has a rightopening 34' providing access to a second pivoting, threaded worm-gearhead 30'. Preferably, the openings 34 and 34' are simply slits, as shownin FIGS. 2 and 3. A first pivoting bracket assembly 28 and a secondpivoting bracket assembly 28' are attached to the connection plate 18directly above the left side support 17 and the right side support 17',respectively. The first drive motor 26 is attached to the first bracketassembly 28. A second drive motor 26' is attached to the second bracketassembly 28'. The first worm-gear 24 extends vertically downward fromthe drive motor 26 engaging the first worm-gear head 30 which has athreaded opening 31 and is rotatably mounted to the left track 19.Similarly, the second worm-gear 24' extends vertically downward from thesecond drive motor 26', engaging the second worm-gear head 30' alsohaving a threaded opening 31' and which is rotatably mounted to theright track 19'. Also as with left track 19, right track 19' is coupledto the rolling platform 22 via rolling means 23. In the preferredembodiment of the invention the rolling means 23 connects the platform22 to the left track 19 and the right track 19' such that the bottom ofthe platform 22 is flush with the bottom level of those tracks.

The first bracket assembly 28 and the second bracket assembly 28' allowfor the proper lift orientation of the first worm-gear 24 to the lefttrack 19 and a second worm-gear 24' to the right track 19',respectively. The first drive motor 26 is synchronized with the seconddrive motor 26' so as to provide a smooth, balanced, lifting force. Thenatural turning of the worm-gears under pressure provides an automatic,simultaneous, fail-safe return to the lower floor level 14 of the lefttrack 19, the right track 19', and the platform 22 if there is a powerfailure. The left track 19 and the right track 19' preferably includeraised sidewall sections 90 so as to eliminate any concerns regardingpossible tipping of a wheelchair 100 positioned on the platform 22. Theplatform 22 can also be provided with a slightly raised section for thesame purpose.

The left track 19 and the right track 19' are fabricated from 4"×2"×1/4"angled-steel that form rails for the roller means 23 of the platform 22.In the preferred embodiment of the invention, the roller means 23 aresimply end sections 91 of roller bars 92, central portions 93 of whichform the platform 22. The end sections 91 of the roller bars 92 arecaptured within the rails of the left track 19 and the right track 19'.The roller bars 92 are themselves adjoined by links or some other wellknown means so as to form the platform 22 and are preferably about 3/8"diameter steel rods. The left track 19 and the right track 19' eachconsists of a short initial straight lower section 60, a first curvedsection 62 that produces the rolling action of the platform 22, and asecond curved section 64, wherein the curvature of the second curvedsection 64 is preferably less than the curvature of the first curvedsection 62. The slight curvature of the second curved section 64maintains the platform 22 in place when the left track 19 and the righttrack 19' are in the upper position where the wheelchair 100 would be atthe top of the stairway 12. The left track 19 and the right track 19'are connected to one another at the end of the lower section 60 by aconnection plate 32 that rests on the floor 14 when the system 10 is inits lowered position. The second curved section 64, shown as a left sidecomponent in FIGS. 2 and 3, and its corresponding right side secondcurved section 64', are preferably designed to follow the dimensions ofa particular stairway and to be connected to that particular stairway.To provide this connection, a pivot hole 70 is drilled through the endof top section 64 in preparation for connecting it to a steel "U"track-support bracket 20. The track support bracket 20 is preferablymade up of 4" wide×1/4" thick steel channels welded together. Thissupport bracket 20 is anchored to a first stairway tread 72 below theupper floor level. Pivot holes 70 and 70' are drilled in the field tomatch the riser height. By placing the support bracket 20 on the firsttread 72 of the stairway 12, the device can be adjusted in the field toaccommodate all standard tread and riser configurations. The left track19 and the right track 19' are suspended above the stairway 12 so thatthey do not have to be perfectly parallel with the stairway 12. Anydifference is corrected for by the resting location of the platform 22.

When the system 10 is in its upper position, the movement of theplatform 22 along the left side track 19 and the right side track 19' isstopped by the last tread of the stairway 12 so that the platform 22 isflush with the top of the stairway 12, the left side track 19, and theright side track 19'. The designs of the left track 19 and of the righttrack 19' are such that, the left track 19 and the right track 19' areraised or lowered, the platform 22 naturally seeks its lowest possibleposition effecting movement of the platform 22 in a smooth rollingaction to its final resting position.

In an alternative design of the system 200 shown in FIGS. 5-7, theportal frame 16 is replaced by the introduction of a combination of aset of side walls including a first side wall 201 and a second side wall201' with one or more hydraulic cylinders 202 used to move the firstside wall 201 and the second side wall 201'. The first left arcuatetrack 19 is coupled to the first side wall 201 and the second rightarcuate track 19' is coupled to the second side wall 201'. As in thedesign of the system 10 previously described, the rolling platform 22remains within the arcuate tracks 19, 19' and operates in essentiallythe same manner. The distinguishing feature of the alternative system200 of the present invention lies in the arrangement of the set of sidewalls in conjunction with the hydraulic cylinders 202. In particular, asillustrated in FIG. 5, which shows a first hydraulic cylinder 202 fullyextended such that the first side wall 201 is raised to a maximumheight. This position of the first side wall 201 results in movement ofthe platform 22 to the top of the stairway 12 via the left arcuate track19 and the right arcuate track 19' (not shown). The wheelchair 100 canthen be moved from the top of the stairway 12 onto the platform 22 fortransport down to the floor 14.

The first side wall 201, like the second side wall 201', includes anupper side wall end 203 that is pivotally affixable to a first pivotbracket 204 having a first pivot pin 205 that keeps the upper side wallend 203 in position while an upper cylinder end 207 of the firsthydraulic cylinder 202 moves a lower side wall end 206 either to araised position, as shown in FIG. 5, or in a lowered positioned, asshown in FIG. 6. It is preferable to have the pivot pin 205 positionedon the pivot bracket 204 so that when the system 200 is in its maximumraised position shown in FIG. 5, the platform 22 is at a slightlydownward angle so as to more easily receive the wheelchair 100. A lowercylinder end 208 of the first hydraulic cylinder 202 is maintained in afixed position by attachment to a lower mounting bracket end 209 of afirst stationary mounting bracket 210. The lower bracket end 209 of thestationary mounting bracket 210 is preferably permitted to rest on thefloor 14 and is optionally secured to a cross bracket 212 that is inturn coupled to a second stationary mounting bracket 210' shown in FIG.7. An upper bracket end 211 of the first stationary bracket 210 iscoupled to the first bracket 204 and to the first side wall 201 by thepivot pin 205. The combination of the cross bracket 212 with the firststationary bracket 210 and the second stationary bracket 210' ispreferably provided in sections so that the spacing between the twostationary brackets 210, 210', can be varied as required by theparticular width of the stairway 12 to which the system 200 is to beattached.

The alternative system 200 shown in FIG. 7 illustrates the use of twohydraulic cylinders, one for movement of the first side wall 201, andone for the second side wall 201'. However, it is contemplated that thesystem 200 may be operable using only one hydraulic cylinder that may beattachable either to the first side wall 201, or to the second side wall201', provided both side walls are securely coupled together.

Although the preferred embodiment of the present invention has beendescribed in some detail herein, it is to be understood that thisdescription is merely illustrative. The inventive apparatus may bemodified in a variety of ways to suit a particular purpose while stillemploying the unique concepts set forth in the SUMMARY.

What is claimed is:
 1. A wheelchair lift system for conveying a wheelchair between a lower floor and an upper floor, comprising:a. a wheelchair-support platform; b. a set of similar arcuate tracks, including a first arcuate track and a second arcuate track, wherein each of said arcuate tracks has an upper end and a lower end; c. means for coupling said wheelchair-support platform to said arcuate tracks; and d. means for raising and lowering said lower end of said first arcuate track and said lower end of said second arcuate track;wherein said wheelchair-support platform when coupled to said arcuate tracks will move along said arcuate tracks in response to a change in elevation of said lower end of each of said arcuate tracks.
 2. The system as claimed in claim 1 wherein said means for coupling said platform to said arcuate tracks includes roller elements connected to said platform and to said arcuate tracks.
 3. The system as claimed in claim 2 wherein each of plurality of said roller elements is connected to said platform and to said arcuate tracks.
 4. The system as claimed in claim 3 wherein each of said plurality of said roller elements is connected to one of said arcuate tracks by an axle.
 5. The system as claimed in claim 1 wherein said upper end of said first arcuate track and said upper end of said second arcuate track are rotatably secured to a track bracket, said bracket being securely mounted below a surface of said upper floor.
 6. The system as claimed in claim 1 with said means for raising and lowering said lower end of said first arcuate track and said lower end of said second arcuate track comprising:a. a reversible drive motor rotatably mounted to a portal frame; b. a worm-gear affixed to a drive shaft of said drive motor; and c. a worm-gear head having a threaded opening engaging said worm-gear and rotatably mounted to said arcuate tracks.
 7. The system as claimed in claim 6 with said portal frame comprising:a. two vertical support members and means for securing first ends of said support members to said lower floor; and b. a connection plate disposed between second ends of said support members and means for attaching said connection plate to said support members.
 8. The system as claimed in claim 1 wherein said system includes a microwave-controlled device for activating said means for raising and lowering said lower end of said first arcuate track and said lower end of said second arcuate track.
 9. A wheelchair lift system for conveying a wheelchair between a lower floor and an upper floor, comprising:a. a wheelchair-support platform including a plurality of roller elements connected to said platform by a support bracket; b. a set of similar arcuate tracks, including a first arcuate track and a second arcuate track, wherein each of said arcuate tracks has an upper end and a lower end, said lower end of each of said arcuate tracks being connected together by a connection plate, and said upper end of each of said arcuate tracks being rotatably secured to a bracket; c. means for raising and lowering said lower end of each of said arcuate tracks comprising a reversible drive motor rotatably mounted to a portal frame, a worm-gear affixed to a drive shaft of said drive motor, and a worm-gear head having a threaded opening engagable with said worm-gear and rotatably mounted to one of said arcuate tracks; and d. means for coupling said wheelchair-support platform to said arcuate tracks including a plurality of roller elements connected to said platform by a support bracket and each of said roller elements connected to said arcuate tracks by an axle;wherein said wheelchair-support platform is designed such that when coupled to said arcuate tracks it will roll along said arcuate tracks in response to a change in elevation of said lower end of each of said arcuate tracks.
 10. A method for conveying an occupied wheelchair between two horizontal levels, said method comprising the steps of:a. placing said occupied wheelchair on a wheelchair-support platform having rolling members in operative engagement with a pair of arcuate tracks, and said platform being suspended between said pair of arcuate tracks; b. activating reversible drive mechanisms to raise or lower said pair of arcuate tracks; c. stopping said rolling wheelchair-support platform by an upper horizontal level when in a raised position and by a connecting means disposed between lower ends of the arcuate tracks when in a lowered position.
 11. The system as claimed in claim 1 with said means for raising and lowering said lower end of said first arcuate track and said lower end of said second arcuate track comprising:a. a set of side walls including a first side wall couplable to said first arcuate track and a second side wall couplable to said second arcuate track; b. a hydraulic cylinder couplable to one of said side walls and to a stationary bracket positioned proximal to said lower floor; and c. means to power said hydraulic cylinder.
 12. The system as claimed in claim 11 wherein said hydraulic cylinder is a first hydraulic cylinder and said stationary bracket is a first stationary bracket, wherein said first hydraulic cylinder is couplable to said first side wall and to said first stationary bracket, the system further comprising a second hydraulic cylinder couplable to said second side wall and to a second stationary bracket positioned proximal to said lower floor, wherein said second hydraulic cylinder is operable by said means to power said first hydraulic cylinder.
 13. The system as claimed in claim 12 further comprising a set of pivot brackets including a first pivot bracket and a second pivot bracket, wherein said first pivot bracket is couplable to an upper first side wall end of said first side wall and to an upper first stationary bracket end of said first stationary bracket, wherein said second pivot bracket is couplable to an upper second side wall end of said second side wall and to an upper second stationary bracket end of said second stationary bracket.
 14. The system as claimed in claim 13 wherein said means to power said first hydraulic cylinder and said second hydraulic cylinder is a pump and motor unit.
 15. The system as claimed in claim 11 wherein the positioning of said first side wall and said second side wall with respect to one another is adjustable.
 16. The system as claimed in claim 11 wherein said first side wall and said second side wall have a height of approximately three feet. 